1. Field of the Invention
This invention relates to blood treatment apparatus and, more particularly, it relates to artificial lungs and similar devices having heat-exchangers for accurately and rapidly regulating the temperature of the blood. A presently preferred embodiment of the present invention is a combination blood oxygenator and heat-exchanger unit affording advantageous economy, safety and compactness features.
2. Description of the Prior Art
Blood oxygenators are used in the course of cardiopulmonary surgery and other procedures, when it is necessary to temporarily employ external mechanical means to perform the function of the lungs or of both the heart and lungs of a patient. It is important to carefully control the temperature of the blood during such procedures. Often the blood temperature is purposely lowered from normal body temperature to a preselected lower temperature during surgery. It is also necessary, at the surgeon's directions, to rapidly return the blood temperature to normal body temperature, while at the same time avoiding trauma to the blood (as by local contact overheating).
A number of prior art devices have been devised for carrying out these functions. Typical of such devices are those disclosed in U.S. Pat. Nos. 3,764,271; 3,769,162 and 3,768,977, as well as other patents discussed therein.
In general, the prior art heat exchanger devices suffer from one or more of the following disadvantages:
1. Relatively low heat exchange effectiveness due to one or more of (a.) insufficient heat-exchange surface for the volume of blood to be treated, (b.) poor flow design, (c.) poorly regulated blood film thickness at the heat exchange surface, or (d.) poor utilization of oxygenator/heat-exchanger design so as to maximize the contact time of the blood with the heat-exchange surface;
2. Danger of contamination of the patient's blood by direct contact with the heat-exchange fluid (typically, water) due to the presence of seals or similar potential leak sites separating the blood from the heat exchange fluid within the interior of the heat-exchange chamber. Such contamination of the blood can lead to serious injury or death of the patient;
3. The possibility of trauma to the blood due to one or more of (a.) turbulent flow, (b.) pockets of stagnation and (c.) flow barriers arising from the design of the equipment.